Neutronic reactor



Feb. 5, 1957 G A. ANDERSON 2,780,596

NEUTRONIC REACTOR Filed NOV. 6, 1950 3 Sheets-Sheet 1 IN V EN TOR.

BY George 4. Kinder-Son ATTORNEY Feb. 5, 1957 5. A. ANDERSON NEUTRONIC REACTOR 3 Sheets-Sheet 2 Filed Nov. 6, 1950 ATTORNEY Feb. 5, 1957 G. A. ANDERSON 2,730,596 NEUTRONIC REACTOR Filed NOV. 6, 1950 I 3 Sheets-Sheet 3 r b E" j I z z z z 6 l3 INVENTOR,

George A. Anderson 4 TTORNEY Fig. is a perspective view of a detail of the fuel element charging mechanism of Fig. 1'.

Referring now to the drawings, the active portion 1 and surrounding reflector 2 together form an elongated cylinder which is retained peripherally by the cylindrical shell 3, preferably formed of austenitic steel. This cylinder is retained at its forward end by an apertured steel retaining plate 4, and at its rearward end by another aper tured steel retaining plate 5.

As best illustrated in Fig. 2, the active portion 1 has a generally hexagonal cross section which is built up of a large number of small hollow prisms 6, preferably in the form of hexagons, as shown in Fig. 4. The basic structural elements or prisms 6 are stacked side against side, and end against end, to form the permanent skeleton structure of the active portion, the hollow interior of the aligned prisms forming fuel channels into which the fuel elements 7 can be inserted. As shown in Fig. 4, each of the outer sides of the prisms 6 are recessed, as at 8, thereby forming outwardly projecting lugs 9 at each of the corners and between each corner. When the prisms 6 are stacked side against side, the lugs 9 of adjoining prisms abut, and the adjacent recessed portions 8 form longitudinally extending passageways through which the cooling medium may flow to cool the permanent structure.

As shown-in Fig. 3, different length prisms are used at the ends of adjacent channels in order to stagger the joints between prisms in the entire assembly. It will be appreciated that use of a large number of small prisms to form the permanent skeleton structure reduces the likelihood of encountering a large temperature difference within any one element and thus reduces thermal stresses.

The fuel elements 7 each comprise an outer hollow open-ended frame 11 having the same cross sectional shape as the prism 6, that is, hexagonal in the example illustrated. The frames 11 maybe of a length comparable to that of the prisms 6 so that a plurality of fuel elements may be charged into a single one of the fuel element channels 10 formed by the aligned prisms 6, as best illustrated in Fig. 3. At each of the outer corners of the frame 11, there is provided an outwardly projecting shoe or runner 12 which extends the entire length of the frame 11. As shown in Fig. 4, the runners 12 cooperate with the inner corners of the associated prism 6 thereby forming longitudinally extending coolant channels 13 through which the coolant may flow to cool the inner surface of the prism 6 and the outer surface of the frames 11.

Supported by and within the frames 11 are a number of spaced rectangular fuel plates 14 containing the fissionable material which supports the chain reaction. The fuel plates 14 are disposed in a vertical longitudinally extending plane so as to provide rectangular cooling channels through which the cooling medium may flow to cool the plates and so as to minimize any tendency the-slabs may have to sag at operating temperatures.

The prisms 6 and the frames 7 are formed of a moderator material, such as beryllium, beryllium oxide, or beryllium carbide, beryllium being preferred. The runners 12 are preferably formed of graphite since graphite is a moderator material, which, in addition, has a selflubricating characteristic which will avoid any tendency for the runners 12 to bind against the inner corners of the prisms 6. The rectangular plates 14 contain a fissionable material, such as U-233, U-235, or Pill-239, and'also contain a moderator material, such as beryllium, beryllium oxide, or beryllium carbide. Preferably, the fuel plates 14 contain the fissionable material and moderator in the form of a beryllium-uranium alloy.

Filling the space between thehexagonal active portion 1 and the cylindrical retaining shell 3 is the reflector region 2 which, for the most part, is solid, and may be built up of a large number of solid blocks of a suitable moderator material, again preferably beryllium. AP-

proximately midway radially in the reflector region, a"- plurality of open channels 20 are left, into which channels f may be removably inserted, if desired, a plurality of rectangular conversion elements 21. Conversion elements 21 will be understood to be formed in a manner similar to that of the fuel elements 7 except that the conversion elements are formed to have a rectangular cross section, as shown. Conversion elements 21 are provided with an outer rectangular frame similar to frame 11 of the fuel elements, this outer frame supporting a plurality of spaced rectangular conversion plates corresponding to the fuel plates 14 of the fuel elements. Instead of fissionable material, however, the plates of the conversion elements 21 contain a material which, upon absorbing a neutron, is converted either to an artificially radioactive isotope which it is desired to produce in quantity or to fissionable material. Thus, it can be considered that the conversion elements 21 form a cylindrical conversion zone circumscribing the active portion and dividing the reflector region 2 into a radially inner and radially outer reflector region.

As may be seen in Fig. 3, a similar conversion zone is provided forwardly and rearwardly of the active portion. This is accomplished by charging into the fuel element channels 10 of the active portion conversion elements 21 of a special design, two of these special conversion elemerits 21' being located at the forward end of each fuel element channel and twobeing located at the rearward end'of each fuel element channel. Special conversion elements 2 1 are identical in every respect with the fuel elements 7 except that the rectangular plates 14 are d1 vided into two longitudinally consecutive sections 23 and 24. The section 23 is formed entirely of moderator material, again preferably beryllium, andthe section 24 contains the material which it is desired to convert to fissionable material or to an artifically radioactive isotope. The two special types of conversion elements 21' are disposed in back to back relationship, as shown in Fig. 3,

30, preferably of low alloy steel, through the steel retain ing plates 4 and 5. The pressure shell 30, in turn, is 4 supported by the massive structure 31 of concrete which also functions as the biological radiation shield for the reactor. The steel retaining plates 4 and 5 are fixedly attached to the inner shell 3, and, at several points around their periphery, these plates 4 and 5 are provided with ears 100 extending radially beyond the inner shell 3 to the pressure shell 30. The steel retaining plates 4 and 5 are held together axially by tie bolts 101, thus confining *the reactor structure axially. While both plates 4 and 5am supported from the pressure shell 30 by way of ears 100, only the one at the rearward end is axially anchored to the pressure shell 30, in order to accommodate axial expansion of the reactor structure.

The cylindrical retaining shell 3 extends forwardly and rearwardly beyond the plates 4 and 5, respectively, and at its forward end, it is left open, whereas, at its rearward end, it is terminated in a closed dome shaped end portion 32. The pressure shell 30 extends longitudinally beyond the termination of the retaining shell 3 in both directions and is closed by dome shaped end portions 33 i at both ends.

sealed opening 103 in the rear end portion 33 of the pressure shell 30. The high pressure helium flowsforwardly, as indicated by the arrows, through the annular space formed between the pressureshell 30 and retaining shell 3 to the point at which the retaining shell 3 termihates. At this point, it reverses and flows rearwardly past a portion of the fuel element charging mechanism and then through the various coolant channel formed in the active portion and reflector. The heated helium is removed from the reactor by means of an exit cooling conduit 104 which passes through the shielding concrete 31, through a seal 105 in the rear end portion 33 of the pressure shell 30, and terminates at a sealed opening 106 in the end portion 32 of the retaining shell 3.

In order to prevent the fuel elements and conversion elements from being blown out of the rear of the reactor by the flowing helium, a fuel retaining grid 40 is provided adjacent the retaining plate Grid has a series of spaced barriers 41 which pass across the apertures in re taining plate 5 which are aligned with the fuel channels and conversion channel The position of retaining grid 40 is controlled by a grid positioning ram 42 which passes through a seal in the rear end portions 32 and 33 of the retaining shell 3 and the pressure shell 30, respectively. The ram 42 terminates in "a piston 71 disposed within a cylinder 72. The position of the piston 71 and grid 40 may thus be remotely controlled by appropriate variation of the fluid pressure within the cylinder 72. As shown, the ram 42 may be surrounded by a stepped shielding plug 62 to inhibit leakage of radiation along the ram.

A series of longitudinally spaced vertically movable control rods 45 are provided in order to control the operating power level of the reactor, these elements extending downwardly through gas tight seals in the steel shells 3 and 30 into wells formed in the active portion of the reactor along a central vertical plane thereof. In order to form these control rod accommodating wells, special prisms 6 and fuel elements 7, having a central aperture therein, are provided along the central vertical plane of the reactor, as indicated in Fig. 2. The control rods 45 are conventional elements and as is well known, they contain a suitable slow neutron absorber, such as, boron or cadmium, which materials have a particularly high slow neutron absorption cross section.

The fuel loading apparatus for the reactor may be considered as consisting of a cartridge positioning mechanism, indicated generally at 50, a cartridge loading mechanism, indicated generally at 51, and a fuel element charging mechanism indicated generally at 52. Briefly, the function of the cartridge positioning mechanism is to transfer loaded fuel cartridges 53 from a longitudinally extending track-way 54, upon which the cartridges slide, to a perpendicular track-way 55, the cartridges being so transferred one at a time by suitable linear movement of a cartridge positioning ram 56. The transferred cartridge 53 is then moved along the trackway 55 by suitable linear movement of a cartridge loading ram 57 of the cartridge loading mechanism 51. The cartridge loading mechanism 51 serves to move the cartridge 53 along the track-way 55, and, at the termination of the track-way, to transfer the cartridge to one-of four magazines 58, which magazines each form an index arm of a rotary device, indicated generally at 59, which device forms a part of the fuel element charging mechanism 52. The function of the fuel element charging mechanism is to rotate the loaded magazine 58 to an appropriate position by suitable rotation of a sleeve shaft 60, and this having been accomplished, 'to transfer the fuel elements and/or conversion elements from the cartridge 53 into the aligned channels of the reactor, this latter operation being effected by suitable reciprocation of a fuel element charging ram 61. The rotatable sleeve shaft 60 and the reciprocable fuel element charging ram 61 are concentric with the reactor and pass first through the dome shaped forward end portion 33 of the steel pressure shell 30 in sealed relationship therewith, and thereafter through a stepped shielding plug 62 in the shielding concrete 31.

The track-ways 54 and 55 are contained within a gas tight enclosure which extends laterally from a point adjacent the forward end of the reactor. At the cartridge loading mechanism 51, this enclosure makes a 90 turn and then extends in a longitudinal direction to a point some distance beyond the rearward end of trackway 54. The cartridge loading ram 57 of the cartridge loading mechanism 51 extends through a suitable seal in the enclosure 70, and the cartridge positioning ram 56 of the cart-ridge positioning mechanism 50 also extends through a suitable seal in the enclosure 70. The reactor end of the enclosure 70 extends through a sealed aperture in the pressure shell 30 and terminates at a sealed opening in the retaining shell 3.

The reciprocable rams 56, 57, and 61 are linearly actuatab'le in any convenient manner externally to the shielding 31. These rams are illustrated as being remotely operable pneumatically or hydraulically by means of pistons 71 disposed within hydraulic cylinders 72. The rotatable sleeve shaft 60 is driven by a motor 73 connected through a gear box 74 to drive pinion gear 75, the pinion gear 75 engaging a gear 76 which is connected to actuate the sleeve shaft 60.

A valve 77 is interposed in the gas tight enclosure 70 so that that portion of the enclosure beyond the valve may be isolated from the remainder of the enclosure and from the high pressure helium system of the reactor proper. A second valve 78 is provided in the enclosure 70 whereby the enclosure may be opened to the atmosphere or sealed from the atmosphere, as desired, the valve 78 being large enough to permit manual insertion of loaded cartridges 53 into the enclosure 70 and onto the track-way 54. It will thus be apparent that that portion of the enclosure 70 beyond the valve 77 serves as a gas lock which may either 'be isolated from the high pressure helium system of the reactor proper and in communication with the atmosphere, or alternatively, may be sealed from the atmosphere and made a part of the high pressure helium system, depending upon the respective positions of the valves 77 and 78.

Also included in the enclosure 70, to the reactor side of the valve 77, is a vertically movable shielding block 80 which may be remotely actuated in any convenient way, again illustrated as by means of a ram 81 terminating in a piston 71 disposed within a hydraulic cylinder 72. The purpose of the shielding block 80, of course, is to prevent radiation streaming along the laterally extending portion of the enclosure 70. The shielding block 80 is in its extreme upper or radiation sealing position during the normal operation of the reactor, and is only lowered, as shown, during the operation of the loading apparatus.

The rotary device 59 of the fuel element charging mechanism 52 is shown in considerable detail in Fig. 5. As there shown, the magazines or index arms 58 are four in number arranged ninety degrees apart, and they are carried by and rotate with the sleeve shaft 60, so that the loaded magazine may be positioned at any angular loading position desired. Each of the arms 58 is provided with a series of radially spaced holes extending therethrough. Each of the holes 90 has associated therewith, in aligned relationship, a finger or plunger 91. Piungers 91 extend from, and are linearly movable with, four radial plunger arms 92, also arranged at 90 degree intervals around the rotary device 59. Two of the plunger arms 92 are attached directly to the fuel element charging ram 61, as indicated at 93, these two arms ex tending through axial slots 94 in the sleeve shaft 60. The other two plunger arms are attached to a circular yoke member 95, which, in turn, is attached to the othertwo plunger arms. By virtue of the above described construction of the rotary device 59, it will be apparent that rotation of sleeve shaft 60 effects rotation of the entire rotary device 59, including plunger arms 92 and index arms 58, and linear movement of the fuel element charging ram 61 effects a corresponding linear movement of plunger arms 92 and plungers 91 relative to the index arms 58;

'Ihea ar ridge t 5.3-1. compri e e s l y.- Q i1,.-h oel s having. a seriesof spaced apertures 96 therein,the-innermostgroupof these apertures being of a shape to accomdate h x go a ue le n 7, nd thenuterms one of these apertures being of a shape to accommodate a conversion element 21.. The,cartridgesfiShave on both edges-of their upper, andjlower; surfaces,a ,plural ity of p ds 11 The p d y fi i g d ls -(nott h wn). which may be provided along the track way 5 5, if desired, to,insure proper alignmentof the cartridges. As. best shown inFig. 5, the magazines or index arms 58 are provided;with upper and lowerslots 98 .into which the upper and lower pads at one edge of the cartridges 53 slidewhen the cartridges are transferred frornthe trackway -.55 te; th .index [arms 158.... :.Th cartr dg a somewhat wider than, the length of the fuel elements and conversion elements, as may be seen in Fig, l. Whenit, is desiredito; reload aparticularchannel of the rea t rr r.apar i ul rsroup f radia lyal gned chan the reactor isshut down, or atleast its power level is reduce t e lo v l e by sui ab etin e ion otcon rol rods 45. The valve 77 isthen checked to insure that it isgclosed, isolating the por ion, of, gas tightenclosure 7 0 beyond this, valve from the, reactor proper, andforming the above-describedgas lock. The gas lock is then preferably purged of radioactivehelium and fill ed,with ai r at,,,atmospheric pressure, after which, the valve. 78 is opened. A sufficient number of cartridges 53 to load an entire channel are .thenmanually inserted within the gas lock and onto the track-wayn54. After each cartridge 53 ;is, inserted, .the cartridge positioning mechanism 50 is actuated, to .move the inserted cartridge. along the .trackway a suflicient distance to make room for the, next cartridge. The r.am 56 of the cartridge,,-positioningmechanism 150 is then withdrawn topermit the insertionof the next cartridge. f

It willbe understood that a large number of sets of identical cartridges 53 :are available ,to the operator, these sets differing from each other in the positioning and spacing, of the slots 96. That is, for each of the various predetermined angular loading positions of the rotary device 59, there is an associated set of cartridges 53, the

spacing and position of the slots 96 of which correspond to-the spacing and position of the radially aligned reactor channels; at that particular angular loading position. At some angular loading positions, only one of the channels wilLbe able to be serviced at one time, whereas, at some other angular loading positions, all of the channels are aligned andare able to be serviced simultaneously. It will beunderstood that the operator has chosen a set of cartridges S S which are appropriate for the particular ohannelor aligned channels which it is desired to service, and that fuel elements 7 and/ or conversion elements 21 had; previously been inscrtedinto the appropriateone or ones of theslots 96 of the cartridges 53.

..- The'traclg-way 54 having been thus loaded with a particular set of cartridges 53, the:valve 78 is closed and the va1ve.77 is opened and the shielding block 80 is lowered, The first loaded cartridge is then transferred to the track-way 55 bysuitable manipulation of the cartridge positioning ram 56. This cartridge 53 is then moved along the track way 55 and transferred to the aligned magazine or index arm 58' by suitable manipulation of the cartridge loading ram 57. The plunger arms 92 andextending plungers 91 are then moved inwardly a short distance, say about two inches, to an intermediate position by a corresponding movement of the fuel element charging ram 61. The effect of moving the charging ram 61 to its intermediate positionis to permit the plungers 9l to,mo.ve part way'into the slots 96 of the cartridge 53 to thereby lock the cartridges at a fixed radial position withrespect to the rotary device 59 and the reactor as a whole; For this purpose, it" will be understood that the innermost'slot 96 of all the cartridges terminates at the end adjacent the plungers-in asection whichco'rresponds 8 q osebct i ed mete eitheinmr nlun er q-that 9", h P ovided between t e. n e m st p un r and h sslwt ohott e i aeram s ot. Thesa trid e 53rh ns b en. u ed n .prz n in th m az n 5 he o y d v ce .5 is Ir a e rby means o leere haft .0 u l t c t ed fue a d o n sr igme emcn s. a e a ne with. cha nel w ic are tobe serviced, The charging ram 61 isthen moved to its innermost position, thereby transferring the elements into the aligned channels of the reactorandejecting the spent elements from-the rear of the channels Inorder that. the h m l m s maybe oeie t re a n d 40, a pr v bui lyb n W r n. byf et e onpf the ram lg The ejected spent element. falls througha ue ele ent di c ar e op i g 1 h wn) i r of the reactor and is removed through a discharge'channel for chemical reprocessing. H H v ,Sleeve shaft 60 is then rotated until the magazine or d x a .-.5. i na th emp y c rt id e. P oj s t ca y dow ar ly in 1 a m n i th openi g 9. cut in the fo ward ex en i rof hecy ea .re i i Psnin 9 .pro d ta ss o a d h e s! SSQ ndi'asa ht c o u simi ariq enl sh eflfl t ro h w i h em ty ca t maybe dis har ed-a. In .std ntopr e m e t t e ar r s a cartridge unloading mechanism (not shown) similar to the cartridge loading .rnechanisrn I 51 may be provided. Th empty. ca rid s e a d. from the do nwa dly ntsisst hs. hdexn rm 8 by ar withdrawing the har ing a ta w t mcst. o it n. w l n e pa e t a th sfhnsu h r s t h t e v vde i e 1 9X m. 5 i a i n with t ash- W5 1 dex. am. m y be lea w th noth l ad d r ilat e mPtv-sa h dseh being d ha ed th ah h the-s h s sav a im n h loading thus described loading process isrepeated until all of. the elements of the radially aligned channels being serviced have been replaced by new, elements, that is, until all at the loaded cartridges 53 have been removed from the track-way 5,4 and discharged as empty cartridges through the opening 99. i i

If it is then desiredto service another radially aligned group of channels associated with a different angular leading" position of the rotary device 59, the entire above described process is repeated utilizing a different set of cartridges}!corresponding to thenew angiilar loading position. When all of the channels which rquire're loading have been thus serviced, the retaining grid 40 is againforced up against retaining plate 5 by actuation of the'rarn 142 the shielding block stl 'is returned toits iipperinost'ipositionf and the valve is closed. The reactor may then be'jr'eturned .to its operating power level by'withdrawal of control rods" 45. As previously brought out, applicants inventive con tirbutionto the 'art is considered't-o lie in the geometry and arrangement of the components'of the' active portion, that is in thehovl fuel elements 7 i and their novel relationshipwith 'the' novel basic prism elements 6' from which the permanent skeleton structure of'the active portion isfQrmed. 'It will be apparent therefore that the'invention is in no way dependent upon the many reactor physics "parameters which'can beva'ried within wide liinits by 't hefdes'igner depending upon the partied lar purp s for whicht he reactor is'intended to be em ploycd. parameters include the ratio of fission} able material to nonfissionable material, the moderating, absorbing, and scattering properties of the particular materials employed, and so forth. The actual size of the reactor and the actual mass of fissionable material required may be'adjusted over a wide range by a suitable choice' 'of these nuclear, parameters, in accordancewith the well-known principles of reactor physics set forth;;i n the previously referred to Goodman publication. Accordingly'Qit beapparent that the'principles oidthe 9 present invention could be applied to very large reactors or to very small reactors. Nevertheless, in the interests of clarity, the design specifications of one example of a reactor incorporating the present invention are fully set forth below:

Hexagonal fuel elements 7 Number 6 per channel in 37 channels=222 T ength 8,5"

Width across flats 7.9

Thickness of fuel plates 14 1 Spacing between fuel plates @i Fuel plate material Be-U alloy, approximately 2% U by weight, U approximately 30% U-235 Since many changes could be made in the above construction and many apparently widely difierent embodiments of this invention could be made without departing from the principles thereof, it is intended that all matter contained in the above description, or shown 10 in the accompanying drawings, shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

A neutronic reactor comprising a permanent skeleton structure forming a plurality of parallel hexagonally shaped channels extending the entire length thereof, said skeleton structure being formed of a plurality of parallel hollow open-ended hexagonal prisms, a plurality of fuel elements removably disposed within said channels, said fuel elements each comprising a hollow open-ended outer hexagonal frame and a plurality of spaced parallel plates containing fissionable material supported by and within said frame, said frames each being provided with an outwardly projecting runner at each corner to provide coolant passageways between the sides of said frames and the adjacent sides of said prisms, the outer sides of said prisms each being provided with a recess extending their entire length to form coolant passageways between the sides of adjacent prisms.

References Cited in the file of this patent UNITED STATES PATENTS 2,518,270 Barr Aug. 8, 1950 FOREIGN PATENTS 861,390 France Oct. 28, 1940 633,339 Great Britain Dec. 12, 1949 OTHER REFERENCES Endeavor (London), vol. 9, April 1950, pages 55, 56 of an article by Cockroft.

Goodman: Science and Engineering of Nuclear Power, vol. 1, p. 187 (1947), Addison Wesley Press, Inc. Cambridge, Mass.

Smyth: Atomic Energy for Military Purposes, pp. 22, 177, August 1945.

Kelly et al.: Phy. Rev. 73, 1135-9 (1948).

Ohlinger: Nucleonics, vol. 5, No. 6, pp. 38-49, December, 1949; vol. 6, No. 2, pp. 54-63, February 1950. 

